Question

问题- 显示由销售员Marshall处理的订单的客户ID，名称和订单总数，但前提是客户名称以General开头或以Electric结尾。排除下单的客户，但也包括不下订单的客户。根据订单总数的降序排序结果，然后按名称升序排序。不要使用LIKE运算符，也不要联接3个表。

问题输出

当前查询

SELECT c.customer_id, 
       c.name, 
       Count(o.order_id) "# of Orders" 
FROM   customers c 
       left join orders o 
              ON c.customer_id = o.customer_id 
WHERE  Substr(c.name, 1, 7) = 'General' 
        OR Substr(c.name, -8) = 'Electric' 
           AND o.order_id IN (SELECT o.order_id
                              FROM   orders o, 
                                     order_items oi 
                              WHERE  o.order_id = oi.order_id 
                                     AND o.salesman_id = (SELECT employee_id 
                                                           FROM   employees 
                                                           WHERE 
                                         last_name = 'Marshall') 
                              GROUP  BY o.order_id 
                              HAVING Count(customer_id) > 1) 
GROUP  BY c.customer_id, 
          c.name;

数据库-

不知道我在做什么错了。

Answer 1

这是一个非常人为的任务...这是一个选择：

select c.customer_id, c.customer_name, count(o.orderid) cnt
from customers c
left join orders o 
    on  o.customer_id = c.customer_id
    and (select last_name from employee e where e.employee_id = o.salesman_id) = 'Marshall'
where substr(c.name, 1, 7) = 'General' or substr(c.name, -8) = 'Electric'
group by c.customer_id, c.customer_name
having count(o.orderid) <> 1

基本思想是left join。 where子句按客户名称过滤-不包含like：您已经拥有了。

要过滤销售人员姓名而没有其他联接，我们在on的{{1}}子句中使用相关子查询。无需携带left join，也无需在order_items中再次选择。

最后，对订单计数的过滤将转到orders子句。

联接和子查询

1 个答案: